1. Field of the Invention
The present invention relates to a logic apparatus and a logic circuit using a single-elemental device which utilizes charging effect of a single elemental charge.
2. Description of the Related Art
A conventional semiconductor integrated circuit device (LSI) is designed according to the function before manufacture, and fabricated by integrating transistors and wiring on a semiconductor chip. For this reason, after manufacture, the LSI cannot change its structure and function. For this reason, many kinds of LSI have been made according to a use.
In contrast, there have been developed a general-purpose chip including LSI such as gate array capable of adding an operation process function met for use with a user after having shipped. However, the degree of freedom of the design of the chip is extremely low. In conventional gate arrays, a user must perform a manufacturing process to form wiring for connecting gates. Therefore, semiconductor manufacturing processes such as evaporation, exposure, developing, and so on is needed. For this reason, a user must have semiconductor production facility.
From such situation, in late years, design concept as referred to as reconfigurable computing (for example, Sueyoshi et al., “information processing” vol. 40 No. 8, page 778) attracts attention as guiding principle of a system design of the next generation. This reconfigurable computing is a technology that can change an operation process function of LSI by a simple operation according to the use desired by a user, if a general purpose semiconductor chip is prepared.
The reconfigurable computing technology differs from a conventional gate array technology that it does not need a semiconductor manufacturing process such as wiring, and enables a change of a logic operation by a simple method such as changes of a program.
If LSI that the reconfigurable computing is possible can be realized, remarkable improvement of process yield can be expected by producing a small kind of basic LSI in large quantities and changing them in many kinds of functions by a simple method.
It is necessary for realizing the reconfigarable computing to provide a function that make an optimized operation store in a logical element as a minimum configuration element for performing a logic operation and rewrite it according to a use. Nonvolatile memories such as EEPROMs have been made research as a logic element to use in the configurable computing (Kume, “Oyo Butsuri” Vol. 65, No. 11, page 1114).
In a flash memory using flash memory cells as EEPROM, when electrons are injected into a floating gate electrode, the threshold of MOSFET increases. Under a certain gate bias condition, it is possible to control ON/OFF of a current by an injection state of electrons. Also, the injected charges can be removed by setting a bias condition properly.
As described above, EEPROM has been looked at as a logic element of an advanced system to which a reconfigurable computing can be applied by virtue of the programmability. However, EEPROM includes problems such as a high drive voltage and an insufficient holding time.
Further, EEPROM can control only ON/OFF of a current, so that optimization of a system (a program) must be performed by merely switching of ON/OFF of the current. For this reason, a great number of elements are required in the formation of a programmable function block.
The object of the present invention is to provide a logic device enabling a reconfigurable computing which can expect high yield by using logic elements having a low drive voltage and a good holding characteristic.